Things You'll Need
Instructions
Examine the piece in daylight, turning it back and forth. Look for a soapy sheen that is almost iridescent. In this light, the color should have a rather sickly tinge of yellow and the glass should be slightly opaque.
Consider the shape and function of the item. Does it match the time period when Vaseline glass was made? Most pieces hint either at Victorian design, with fussy crinkled edges and cut-glass decoration, or they point towards the Art Deco with angular, stepped motifs. If an item seems to come from a much earlier or much later time period, then it's probably not Vaseline glass.
Dim the lights and test the item with ultraviolet. Sites such as Crime Prevention Products offer a wide range of affordable U.V. lights. If the item is indeed Vaseline glass, then it will fluoresce a strong, bright green.